Distributor is One Tooth off 66 300 hp

[Fred K.]

John, another question on my 66 327, 300 hp: I discovered what I think is a plug wiring problem. Looking at all the diagrams I can get my hand on it looks to me that the number 1 cylinder is front driver's side. And the plug wire from the distributor to that cylinder should be the one between the dwell setting window and the vacuum advance. (# 1 and #2 plug wires cross over each other leaving the distributor. The engine was rebuilt by a quality builder but it looks like he does not have the #1 and #2 wires going to the right cylinders). Problem - when I switch the wires to where they should be I cannot set the timing at 6 BTC because the vacuum advance housing hits up against the intake manifold. So, do I need to pull the distributor and get thing realigned? The car runs but it is a little bit rough at ideal RPMs. Your thoughts please.

[John H.]

Re: Usable Fuel Pump For 66 Sb

John, another question on my 66 327, 300 hp: I discovered what I think is a plug wiring problem. Looking at all the diagrams I can get my hand on it looks to me that the number 1 cylinder is front driver's side. And the plug wire from the distributor to that cylinder should be the one between the dwell setting window and the vacuum advance. (# 1 and #2 plug wires cross over each other leaving the distributor. The engine was rebuilt by a quality builder but it looks like he does not have the #1 and #2 wires going to the right cylinders). Problem - when I switch the wires to where they should be I cannot set the timing at 6 BTC because the vacuum advance housing hits up against the intake manifold. So, do I need to pull the distributor and get thing realigned? The car runs but it is a little bit rough at ideal RPMs. Your thoughts please.

Fred -

Distributor housing/vacuum advance can orientation and plug wire indexing are only critical for Corvettes, so many builders don't pay a lot of attention to it. You need to pull the distributor up and re-stab it one tooth clockwise - that will move it away from the #8 intake runner and closer to the plug wire support (one tooth is about 27* of distributor rotor rotation).

If that ends up being too far (VAC hits plug wire support), you'll need to pull the distributor and re-orient the drive gear 180* on the mainshaft - that will get you 14* of rotor rotation instead of 27* from your original position. This occurs frequently with aftermarket camshafts, as aftermarket cam grinders generally pay no attention to indexing the camshaft drive pin at the front to the distributor drive gear at the rear (GM DID).

When you're done, the distributor orientation and plug wire indexing in the cap should appear like the photo below.


dist2.jpg

[Joe R.]

Re: Usable Fuel Pump For 66 Sb

Hi John,

Does your picture apply to a BB engine too?

Thanks,
Joe

[William C.]

Re: Usable Fuel Pump For 66 Sb

Can't speak for John, but the Chevrolet practice in this area was the same for BB and smallblock engines. Most of the distributor parts will also interchange.

[Joseph M.]

Re: Usable Fuel Pump For 66 Sb

I had a 70 454 judged and there's a notation regarding the distributor being off one tooth. Does this "one tooth off" affect performance in any way. The car seems to run fine.

[Terry M.]

Re: Usable Fuel Pump For 66 Sb

I had a 70 454 judged and there's a notation regarding the distributor being off one tooth. Does this "one tooth off" affect performance in any way. The car seems to run fine.

It won't affect performance unless you can not get the distributor to the proper initial timing due to the vacuum advance hitting the distributor shield mount or the intake/carburetor.

[William C.]

Re: Usable Fuel Pump For 66 Sb

Only appearance if, as Terry notes you can time it properly. A Sharp judge may notice it is off position.

[Jim C.]

Re: Usable Fuel Pump For 66 Sb

Fred -

Distributor housing/vacuum advance can orientation and plug wire indexing are only critical for Corvettes, so many builders don't pay a lot of attention to it. You need to pull the distributor up and re-stab it one tooth clockwise - that will move it away from the #8 intake runner and closer to the plug wire support (one tooth is about 27* of distributor rotor rotation).

If that ends up being too far (VAC hits plug wire support), you'll need to pull the distributor and re-orient the drive gear 180* on the mainshaft - that will get you 14* of rotor rotation instead of 27* from your original position. This occurs frequently with aftermarket camshafts, as aftermarket cam grinders generally pay no attention to indexing the camshaft drive pin at the front to the distributor drive gear at the rear (GM DID).

When you're done, the distributor orientation and plug wire indexing in the cap should appear like the photo below.


[ATTACH]47146[/ATTACH]

Fred, it is a royal PIA to get this right. Often you end up skipping two teeth on the gear when trying to reset it . Don't give up and it will eventually end up as in Johns picture with all the room needed for proper adjustment. Make sure your plug wires are located correctly on the distributor cap per the shop manual.
Just realize it may take several attempts to find the proper tooth on the dist. Hang in there with it.

[Timothy B.]

Re: Usable Fuel Pump For 66 Sb

Put the car in third gear and rock it until the rotor is pointing forward at 12 o'clock position then lift the distributor and walk it around one tooth clockwise.

You can lift the distributor just enough the disengage the camshaft gear and walk it one tooth. Turning clockwise most times the oil pump shaft will follow, if it does not walk it back or forward to find it then walk it around one tooth at a time droping it down engaging the oil drive on each tooth and it will move around with you. It only takes a minute to walk the distributor around the complete 360* so don't be afraid to try, you have the starting point as 12 o'clock.

After you have determined the correct position, advance or retard the distributor until the points just begin to open and sung it down. Don't attempt to run the engine unless the hold down clamp is snug, that distributor will walk up out of the motor in short order.

[Michael W.]

Re: Usable Fuel Pump For 66 Sb

I had a 70 454 judged and there's a notation regarding the distributor being off one tooth. Does this "one tooth off" affect performance in any way. The car seems to run fine.

The judge should have noted instead that the plug wire installation on the dist. cap was off by one position from OEM. The wires and the rotor would need to all be bumped over one position in order to 'fix' it.

The 'off one tooth' thing confuses the crap out of many, needlessly.

[Fred K.]

Re: Usable Fuel Pump For 66 Sb

Moving the distributor one tooth did the job. One more question: When I check the vacuum from the carb to the vacuum advance can I get a max, at 500 rpms, of 10 hg. Is this adequate vacuum? I do not get any timing advance, at idle, from the 6 degree setting with the vacuum line plugged. I am thinking that the vacuum advance can diaphragm is bad. Advice please.

[William C.]

Re: Usable Fuel Pump For 66 Sb

Use a vacuum pump directly on the can and see if it pulls advance with a hand vac pump. I don't remember if '66 is when they started using "ported" vacuum or not, but if so, the throttle blades cover the vacuum port at idle and you don't get vac advance until the throttles are opened.